That the cancer chemopreventive agent oltipraz modulates the catalytic activity of cytochrome P450, using selective in vivo probes, the effects of acute oral dosing w/lotipraz on individual cytochrome P450 (CYP) isoforms (CYP1A2, CYP2A6, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A) in healthy subjects.